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Posukh OL, Maslova EA, Danilchenko VY, Zytsar MV, Orishchenko KE. Functional Consequences of Pathogenic Variants of the GJB2 Gene (Cx26) Localized in Different Cx26 Domains. Biomolecules 2023; 13:1521. [PMID: 37892203 PMCID: PMC10604905 DOI: 10.3390/biom13101521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/08/2023] [Accepted: 10/10/2023] [Indexed: 10/29/2023] Open
Abstract
One of the most common forms of genetic deafness has been predominantly associated with pathogenic variants in the GJB2 gene, encoding transmembrane protein connexin 26 (Cx26). The Cx26 molecule consists of an N-terminal domain (NT), four transmembrane domains (TM1-TM4), two extracellular loops (EL1 and EL2), a cytoplasmic loop, and a C-terminus (CT). Pathogenic variants in the GJB2 gene, resulting in amino acid substitutions scattered across the Cx26 domains, lead to a variety of clinical outcomes, including the most common non-syndromic autosomal recessive deafness (DFNB1A), autosomal dominant deafness (DFNA3A), as well as syndromic forms combining hearing loss and skin disorders. However, for rare and poorly documented variants, information on the mode of inheritance is often lacking. Numerous in vitro studies have been conducted to elucidate the functional consequences of pathogenic GJB2 variants leading to amino acid substitutions in different domains of Cx26 protein. In this work, we summarized all available data on a mode of inheritance of pathogenic GJB2 variants leading to amino acid substitutions and reviewed published information on their functional effects, with an emphasis on their localization in certain Cx26 domains.
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Affiliation(s)
- Olga L. Posukh
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Ekaterina A. Maslova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Valeriia Yu. Danilchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
| | - Marina V. Zytsar
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
| | - Konstantin E. Orishchenko
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia; (E.A.M.); (V.Y.D.); (M.V.Z.); (K.E.O.)
- Novosibirsk State University, 630090 Novosibirsk, Russia
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Serpen JY, Presley W, Beil A, Armenti ST, Johnson K, Mian SI, Innis JW, Prasov L. A Novel 13q12 Microdeletion Associated with Familial Syndromic Corneal Opacification. Genes (Basel) 2023; 14:1034. [PMID: 37239394 PMCID: PMC10218699 DOI: 10.3390/genes14051034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/21/2023] [Accepted: 04/23/2023] [Indexed: 05/28/2023] Open
Abstract
Progressive corneal opacification can result from multiple etiologies, including corneal dystrophies or systemic and genetic diseases. We describe a novel syndrome featuring progressive epithelial and anterior stromal opacification in a brother and sister and their mildly affected father, with all three family members having sensorineural hearing loss and two also with tracheomalacia/laryngomalacia. All carried a 1.2 Mb deletion at chromosome 13q12.11, with no other noteworthy co-segregating variants identified on clinical exome or chromosomal microarray. RNAseq analysis from an affected corneal epithelial sample from the proband's brother revealed downregulation of XPO4, IFT88, ZDHHC20, LATS2, SAP18, and EEF1AKMT1 within the microdeletion interval, with no notable effect on the expression of nearby genes. Pathway analysis showed upregulation of collagen metabolism and extracellular matrix (ECM) formation/maintenance, with no significantly down-regulated pathways. Analysis of overlapping deletions/variants demonstrated that deleterious variants in XPO4 were found in patients with laryngomalacia and sensorineural hearing loss, with the latter phenotype also being a feature of variants in the partially overlapping DFNB1 locus, yet none of these had reported corneal phenotypes. Together, these data define a novel microdeletion-associated syndromic progressive corneal opacification and suggest that a combination of genes within the microdeletion may contribute to ECM dysregulation leading to pathogenesis.
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Affiliation(s)
- Jasmine Y. Serpen
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - William Presley
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Adelyn Beil
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Stephen T. Armenti
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kayla Johnson
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Shahzad I. Mian
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
| | - Jeffrey W. Innis
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lev Prasov
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109, USA
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Jaradat R, Li X, Chen H, Stathopulos PB, Bai D. The Hydrophobic Residues in Amino Terminal Domains of Cx46 and Cx50 Are Important for Their Gap Junction Channel Ion Permeation and Gating. Int J Mol Sci 2022; 23:ijms231911605. [PMID: 36232905 PMCID: PMC9570504 DOI: 10.3390/ijms231911605] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 11/09/2022] Open
Abstract
Lens gap junctions (GJs) formed by Cx46 and Cx50 are important to keep lens transparency. Functional studies on Cx46 and Cx50 GJs showed that the Vj-gating, single channel conductance (γj), gating polarity, and/or channel open stability could be modified by the charged residues in the amino terminal (NT) domain. The role of hydrophobic residues in the NT on GJ properties is not clear. Crystal and cryo-EM GJ structures have been resolved, but the NT domain structure has either not been resolved or has showed very different orientations depending on the component connexins and possibly other experimental conditions, making it difficult to understand the structural basis of the NT in Vj-gating and γj. Here, we generated missense variants in Cx46 and Cx50 NT domains and studied their properties by recombinant expression and dual whole-cell patch clamp experiments on connexin-deficient N2A cells. The NT variants (Cx46 L10I, N13E, A14V, Q15N, and Cx50 I10L, E13N, V14A, N15Q) were all able to form functional GJs with similar coupling%, except Cx46 N13E, which showed a significantly reduced coupling%. The GJs of Cx46 N13E, A14V and Cx50 E13N, N15Q showed a reduced coupling conductance. Vj-gating of all the variant GJs were similar to the corresponding wild-type GJs except Cx46 L10I. The γj of Cx46 N13E, A14V, Cx50 E13N, and N15Q GJs was reduced to 51%, 82%, 87%, and 74%, respectively, as compared to their wild-type γjs. Structural models of Cx46 L10I and A14V predicted steric clashes between these residues and the TM2 residues, which might be partially responsible for our observed changes in GJ properties. To verify the importance of hydrophobic interactions, we generated a variant, Cx50 S89T, which also shows a steric clash and failed to form a functional GJ. Our experimental results and structure models indicate that hydrophobic interactions between the NT and TM2 domain are important for their Vj-gating, γj, and channel open stability in these and possibly other GJs.
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Jabbarpour N, Saei H, Jabbarpoor Bonyadi MH, Bonyadi M. Identification of novel cis-mutations in the GJA8 gene in a 3-generation Iranian family with autosomal dominant congenital nuclear cataract. Ophthalmic Genet 2022; 43:609-614. [PMID: 35726576 DOI: 10.1080/13816810.2022.2089363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Cataract is mainly due to the presence of high molecular weight protein, which disrupts the normal function of the lens. Pathogenic variants in Gap Junction protein alpha-8 (GJA8) have been associated with autosomal dominant congenital nuclear cataract. In general, mutations in those genes that have important functions in lens development lead to congenital cataract. METHODS We conducted whole-exome sequencing (WES) in a four-year-old male patient referred to the genetic center for genetic analysis. He had developed cataract at an early age. DNAs were extracted from the blood samples of all family members and subjected to PCR-Sanger sequencing to confirm the WES results. RESULTS WES analysis on the proband revealed two mutations in the GJA8 gene (c.G12C, c.G58A). His mother, alongside several other members of the third-generation family, had developed cataract. Sanger sequencing of the interested regions showed that these two mutations were co-segregated in all affected members. However, none of the healthy individuals carried these mutations confirming that these two mutations are located in the same allele (complex allele). Bioinformatics analysis of the mutated GJA8 RNA and protein structure confirmed the pathogenicity of the cis-mutations. CONCLUSIONS Genetic segregation analysis in a three-generation family and also bioinformatics analysis showed that the complex-allele containing c.G12C+c.G58A mutations in the GJA8 gene is a pathogenic variant that causes autosomal-dominant congenital nuclear cataract.
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Affiliation(s)
- Neda Jabbarpour
- Animal Biology Department, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Hassan Saei
- Laboratoire des Maladies Rénales Héréditaires, Institut Imagine, Université de Paris-Cité, Paris, France
| | | | - Mortaza Bonyadi
- Center of Excellence for Biodiversity, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
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Hassan AY, Yousaf S, Levin MR, Saeedi OJ, Riazuddin S, Alexander JL, Ahmed ZM. Novel Homozygous Missense Variant in GJA3 Connexin Domain Causing Congenital Nuclear and Cortical Cataracts. Int J Mol Sci 2021; 23:240. [PMID: 35008666 PMCID: PMC8745576 DOI: 10.3390/ijms23010240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/17/2021] [Accepted: 12/24/2021] [Indexed: 11/29/2022] Open
Abstract
Congenital cataracts (CC) are responsible for approximately one-tenth of childhood blindness cases globally. Here, we report an African American family with a recessively inherited form of CC. The proband demonstrated decreased visual acuity and bilateral cataracts, with nuclear and cortical cataracts in the right and left eye, respectively. Exome sequencing revealed a novel homozygous variant (c.563A > G; p.(Asn188Ser)) in GJA3, which was predicted to be pathogenic by structural analysis. Dominantly inherited variants in GJA3 are known to cause numerous types of cataracts in various populations. Our study represents the second case of recessive GJA3 allele, and the first report in African Americans. These results validate GJA3 as a bona fide gene for recessively inherited CC in humans.
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Affiliation(s)
- Abdullah Y. Hassan
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (A.Y.H.); (S.Y.); (S.R.)
| | - Sairah Yousaf
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (A.Y.H.); (S.Y.); (S.R.)
| | - Moran R. Levin
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (M.R.L.); (O.J.S.)
| | - Osamah J. Saeedi
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (M.R.L.); (O.J.S.)
| | - Saima Riazuddin
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (A.Y.H.); (S.Y.); (S.R.)
- Department of Molecular Biology and Biochemistry, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Janet L. Alexander
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (M.R.L.); (O.J.S.)
| | - Zubair M. Ahmed
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (A.Y.H.); (S.Y.); (S.R.)
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Maryland, Baltimore, MD 21201, USA; (M.R.L.); (O.J.S.)
- Department of Molecular Biology and Biochemistry, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
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Gosak M, Gojić D, Spasovska E, Hawlina M, Andjelic S. Cataract Progression Associated with Modifications in Calcium Signaling in Human Lens Epithelia as Studied by Mechanical Stimulation. Life (Basel) 2021; 11:life11050369. [PMID: 33919270 PMCID: PMC8143283 DOI: 10.3390/life11050369] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/14/2021] [Accepted: 04/19/2021] [Indexed: 12/18/2022] Open
Abstract
Ca2+ homeostasis and signaling disturbances are associated with lens pathophysiology and are involved in cataract formation. Here, we explored the spatiotemporal changes in Ca2+ signaling in lens epithelial cells (LECs) upon local mechanical stimulation, to better understand the LECs’ intercellular communication and its association with cataractogenesis. We were interested in if the progression of the cataract affects the Ca2+ signaling and if modifications of the Ca2+ homeostasis in LECs are associated with different cataract types. Experiments were done on the human postoperative anterior lens capsule (LC) preparations consisting of the monolayer of LECs on the basement membrane. Our findings revealed that the Ca2+ signal spreads radially from the stimulation point and that the amplitude of Ca2+ transients decreases with increasing distance. It is noteworthy that a comparison of signaling characteristics with respect to the degree of cataract progression revealed that, in LCs from more developed cataracts, the Ca2+ wave propagates faster and the amplitudes of Ca2+ signals are lower, while their durations are longer. No differences were identified when comparing LCs with regard to the cataract type. Moreover, experiments with Apyrase have revealed that the Ca2+ signals are not affected by ATP-dependent paracrine communication. Our results indicated that cataract progression is associated with modifications in Ca2+ signaling in LECs, suggesting the functional importance of altered Ca2+ signaling of LECs in cataractogenesis.
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Affiliation(s)
- Marko Gosak
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia;
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
| | - Dajana Gojić
- Eye Hospital, University Medical Centre, 1000 Ljubljana, Slovenia; (D.G.); (E.S.); (M.H.)
| | - Elena Spasovska
- Eye Hospital, University Medical Centre, 1000 Ljubljana, Slovenia; (D.G.); (E.S.); (M.H.)
| | - Marko Hawlina
- Eye Hospital, University Medical Centre, 1000 Ljubljana, Slovenia; (D.G.); (E.S.); (M.H.)
| | - Sofija Andjelic
- Eye Hospital, University Medical Centre, 1000 Ljubljana, Slovenia; (D.G.); (E.S.); (M.H.)
- Correspondence:
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Brink PR, Valiunas V, White TW. Lens Connexin Channels Show Differential Permeability to Signaling Molecules. Int J Mol Sci 2020; 21:ijms21186943. [PMID: 32971763 PMCID: PMC7555617 DOI: 10.3390/ijms21186943] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/18/2020] [Accepted: 09/19/2020] [Indexed: 12/12/2022] Open
Abstract
Gap junction channels mediate the direct intercellular passage of small ions as well as larger solutes such as second messengers. A family of proteins called connexins make up the subunits of gap junction channels in chordate animals. Each individual connexin forms channels that exhibit distinct permeability to molecules that influence cellular signaling, such as calcium ions, cyclic nucleotides, or inositol phosphates. In this review, we examine the permeability of connexin channels containing Cx43, Cx46, and Cx50 to signaling molecules and attempt to relate the observed differences in permeability to possible in vivo consequences that were revealed by studies of transgenic animals where these connexin genes have been manipulated. Taken together, these data suggest that differences in the permeability of individual connexin channels to larger solutes like 3',5'-cyclic adenosine monophosphate (cAMP) and inositol 1,4,5-trisphosphate (IP3) could play a role in regulating epithelial cell division, differentiation, and homeostasis in organs like the ocular lens.
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Valiunas V, White TW. Connexin43 and connexin50 channels exhibit different permeability to the second messenger inositol triphosphate. Sci Rep 2020; 10:8744. [PMID: 32457413 PMCID: PMC7251084 DOI: 10.1038/s41598-020-65761-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 05/07/2020] [Indexed: 11/12/2022] Open
Abstract
Gap junction channels made of different connexins have distinct permeability to second messengers, which could affect many cell processes, including lens epithelial cell division. Here, we have compared the permeability of IP3 and Ca2+ through channels made from two connexins, Cx43 and Cx50, that are highly expressed in vertebrate lens epithelial cells. Solute transfer was measured while simultaneously monitoring junctional conductance via dual whole-cell/perforated patch clamp. HeLa cells expressing Cx43 or Cx50 were loaded with Fluo-8, and IP3 or Ca2+ were delivered via patch pipette to one cell of a pair, or to a monolayer while fluorescence intensity changes were recorded. Cx43 channels were permeable to IP3 and Ca2+. Conversely, Cx50 channels were impermeable to IP3, while exhibiting high permeation of Ca2+. Reduced Cx50 permeability to IP3 could play a role in regulating cell division and homeostasis in the lens.
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Affiliation(s)
- Virginijus Valiunas
- The Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, NY, 11794, USA
| | - Thomas W White
- The Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, NY, 11794, USA.
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Gu S, Biswas S, Rodriguez L, Li Z, Li Y, Riquelme MA, Shi W, Wang K, White TW, Reilly M, Lo WK, Jiang JX. Connexin 50 and AQP0 are Essential in Maintaining Organization and Integrity of Lens Fibers. Invest Ophthalmol Vis Sci 2020; 60:4021-4032. [PMID: 31560767 PMCID: PMC6779290 DOI: 10.1167/iovs.18-26270] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Purpose Connexins and aquaporins play essential roles in maintaining lens homeostasis and transparency and there is a close physical and functional relationship between these two proteins. Aquaporin 0 (AQP0), in addition to its role in water transport in the lens, acts as a cell-cell adhesion molecule. Recently, we showed a new role of connexin (Cx) 50 in mediating cell-cell adhesion. However, the cooperative roles of these two proteins in the lens in vivo have not been reported. Methods We generated an AQP0/Cx50 double knockout (dKO) mouse model. Light, fluorescence, transmission thin section, and freeze-fracture electron microscopy, as well as wheat germ agglutinin and phalloidin labeling were used to evaluate lens structure. Mechanical properties of lenses were determined by mechanical compression testing. Results DKO mice exhibited small eyes and lenses with severe cataracts, along with lens posterior defects, including posterior capsule rupture. The dKO mouse lenses had severe structural disruption associated with increased spaces between lens fiber cells when compared with wild-type lenses or lenses deficient in either Cx50 or AQP0. DKO mice also exhibited greater reduction in lens size compared with Cx50 KO mice. Gap-junction plaque size was greatly decreased in cortical fiber cells in dKO mice. Moreover, lens stiffness and elasticity were completely diminished, exhibiting a gelatinous texture in adult dKO mice. Conclusions This novel mouse model reveals that Cx50 and AQP0 play an important role in mediating cell-cell adhesion function in the lens fiber cells and their deficiency impairs lens fiber organization, integrity, mechanical properties, and lens development.
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Affiliation(s)
- Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Sondip Biswas
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, Georgia, United States
| | - Luis Rodriguez
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Zhen Li
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Yuting Li
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Wen Shi
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States.,The Second Xiangya Hospital, Central South University, Changsha, China
| | - Ke Wang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, United States
| | - Matthew Reilly
- Department of Biomedical Engineering, The Ohio State University College of Engineering, Columbus, Ohio, United States
| | - Woo-Kuen Lo
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, Georgia, United States
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, Texas, United States
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10
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Valiunas V, Brink PR, White TW. Lens Connexin Channels Have Differential Permeability to the Second Messenger cAMP. Invest Ophthalmol Vis Sci 2019; 60:3821-3829. [PMID: 31529078 PMCID: PMC6750889 DOI: 10.1167/iovs.19-27302] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 08/13/2019] [Indexed: 01/14/2023] Open
Abstract
Purpose Gap junction channels exhibit connexin specific biophysical properties, including the selective intercellular passage of larger solutes, such as second messengers. Here, we have examined the cyclic nucleotide permeability of the lens connexins, which could influence events like epithelial cell division and differentiation. Methods We compared the cAMP permeability through channels composed of Cx43, Cx46, or Cx50 using simultaneous measurements of junctional conductance and intercellular transfer. For cAMP detection, the recipient cells were transfected with a cAMP sensor gene, the cyclic nucleotide-modulated channel from sea urchin sperm (SpIH). cAMP was introduced via patch pipette into the cell of the pair that did not express SpIH. SpIH-derived currents were recorded from the other cell of a pair that expressed SpIH. cAMP permeability was also directly visualized in transfected cells using a chemically modified fluorescent form of the molecule. Results cAMP transfer was observed for homotypic Cx43 channels over a wide range of junctional conductance. Homotypic Cx46 channels also transferred cAMP, but permeability was reduced compared with Cx43. In contrast, homotypic Cx50 channels exhibited extremely low permeability to cAMP, when compared with either Cx43, or Cx46. Conclusions These data show that channels made from Cx43 and Cx46 result in the intercellular delivery of cAMP in sufficient quantity to activate cyclic nucleotide-modulated channels. The data also suggest that the greatly reduced cAMP permeability of Cx50 channels could play a role in the regulation of cell division in the lens.
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Affiliation(s)
- Virginijus Valiunas
- The Renaissance Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, New York, United States
| | - Peter R. Brink
- The Renaissance Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, New York, United States
| | - Thomas W. White
- The Renaissance Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook, New York, United States
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11
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Hadrami M, Bonnet C, Veten F, Zeitz C, Condroyer C, Wang P, Biya M, Sidi Ahmed MA, Zhang Q, Cheikh S, Audo I, Petit C, Houmeida A. A novel missense mutation of GJA8 causes congenital cataract in a large Mauritanian family. Eur J Ophthalmol 2018; 29:621-628. [PMID: 30373400 DOI: 10.1177/1120672118804757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE OF THE STUDY Inborn lens opacity is the most frequent cause of childhood blindness. In this study, we aimed to define the presumed genetic cause of a congenital cataract present in a Mauritanian family over the last nine generations. METHODS A family history of the disease and eye examination were carried out for the family members. Next-generation sequencing using a panel of 116 cataract underlying genes was selectively conducted on the proband's DNA. Nucleotide and amino acid changes and their impact on the phenotype were evaluated using various data analyzing software. RESULTS Congenital nuclear cataract, with autosomal dominant mode, was observed in the family. All patients had consequences on their vision in the first 2 years of life. Genetic screening revealed a new mutation c.166A>C (p.Thr56Pro) in GJA8, encoding the Cx50 α-connexin protein. This mutation co-segregated in all patients and was not observed in the unaffected family members and controls. The predicted secondary structure impacted by p.Thr56Pro revealed a localized disruption, in the first extra membrane loop of the wild-type sheet, which is replaced in the mutant protein by a turn then a coil. This conformational change was functionally predicted as probably damaging. CONCLUSION A new mutation (c.166A>C) in GJA8 underlying a nuclear congenital cataract was identified in this study. Its segregation with the phenotype might be useful as a predicting marker of the disease.
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Affiliation(s)
- Mouna Hadrami
- Unité de Recherche sur les Biomarqueurs dans la Population Mauritanienne, Université des Sciences de Technologies et de médecine (USTM), Nouakchott, Mauritanie
| | - Crystel Bonnet
- Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, Paris, France.,UMRS 1120, Institut National de la Santé et de la Recherche Médicale, Paris, France.,Complexité du Vivant, UPMC Université Paris 06, Sorbonne Universités, Paris, France
| | - Fatimetou Veten
- Unité de Recherche sur les Biomarqueurs dans la Population Mauritanienne, Université des Sciences de Technologies et de médecine (USTM), Nouakchott, Mauritanie
| | - Christina Zeitz
- Institut de la Vision, CNRS-INSERM, Sorbonne Université, Paris, France
| | | | - Panfeng Wang
- Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Mohamed Biya
- Unité de Recherche sur les Biomarqueurs dans la Population Mauritanienne, Université des Sciences de Technologies et de médecine (USTM), Nouakchott, Mauritanie
| | | | - Qingjiong Zhang
- Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Sidi Cheikh
- Service Ophtalmologie, Centre Hospitalier National, Nouakchott, Mauritanie
| | - Isabelle Audo
- Institut de la Vision, CNRS-INSERM, Sorbonne Université, Paris, France.,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, DHU Sight Restore, INSERM-DHOS CIC 1423, Paris, France.,Institute of Ophthalmology, University College of London, London, UK
| | - Christine Petit
- Syndrome de Usher et Autres Atteintes Rétino-Cochléaires, Institut de la Vision, Paris, France.,UMRS 1120, Institut National de la Santé et de la Recherche Médicale, Paris, France.,Complexité du Vivant, UPMC Université Paris 06, Sorbonne Universités, Paris, France.,Unité de Génétique et Physiologie de l'Audition, Institut Pasteur, Paris, France.,Collège de France, Paris, France
| | - Ahmed Houmeida
- Unité de Recherche sur les Biomarqueurs dans la Population Mauritanienne, Université des Sciences de Technologies et de médecine (USTM), Nouakchott, Mauritanie
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12
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Berry V, Ionides ACW, Pontikos N, Moghul I, Moore AT, Cheetham ME, Michaelides M. Whole-genome sequencing reveals a recurrent missense mutation in the Connexin 46 (GJA3) gene causing autosomal-dominant lamellar cataract. Eye (Lond) 2018; 32:1661-1668. [PMID: 29934635 PMCID: PMC6189195 DOI: 10.1038/s41433-018-0154-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/24/2018] [Accepted: 05/03/2018] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Congenital cataract, opacification of the ocular lens, is clinically and genetically a heterogeneous childhood disease. In this study we aimed to identify the underlying genetic cause of isolated autosomal-dominant lamellar cataract in a multi-generation English family. METHODS Whole-genome sequencing (WGS) was undertaken in two affected subjects and one unaffected individual. Segregation analysis was performed and a known cataract-causing mutation was identified. Segregation was further validated by sanger sequencing in the entire pedigree. RESULTS A heterozygous mutation c.7 G > T; p.D3Y was identified in an NH2-terminal region of the gap junction protein GJA3 and found to co-segregate with disease. CONCLUSION We have identified a recurrent mutation in GJA3 in a large British pedigree causing the novel phenotype of autosomal-dominant congenital lamellar cataract. Previously, p.D3Y was found in a Hispanic family causing pulverulent cataract. WGS proved an efficient method to find the underlying molecular cause in this large family, which could not be mapped due to uninformative markers.
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Affiliation(s)
- Vanita Berry
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK.
| | | | - Nikolas Pontikos
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
- UCL Genetics Institute, University College London, London, WC1E 6BT, UK
| | - Ismail Moghul
- UCL Cancer Institute, University College London, London, WC1E 6DD, UK
| | - Anthony T Moore
- Moorfields Eye Hospital, London, EC1V 2PD, UK
- Ophthalmology Department, University of California School of Medicine, San Francisco, CA, 94158, USA
| | | | - Michel Michaelides
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK.
- Moorfields Eye Hospital, London, EC1V 2PD, UK.
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13
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Hu Z, Shi W, Riquelme MA, Shi Q, Biswas S, Lo WK, White TW, Gu S, Jiang JX. Connexin 50 Functions as an Adhesive Molecule and Promotes Lens Cell Differentiation. Sci Rep 2017; 7:5298. [PMID: 28706245 PMCID: PMC5509658 DOI: 10.1038/s41598-017-05647-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 06/01/2017] [Indexed: 11/25/2022] Open
Abstract
Connexins play essential roles in lens homeostasis and development. Here, we identified a new role for Cx50 that mediates cell-cell adhesion function. Cx50 enhanced the adhesive capability of AQP0. Interestingly, the expression of Cx50 alone promoted cell adhesion at a comparable level to AQP0; however, this cell adhesive function was not observed with other lens connexins, Cx43 and Cx46. Moreover, the adhesive property occurred in both homotypic with Cx50 expressed in both pairing cells and heterotypic with Cx50 in only one pairing cell, and this function appears to be unrelated to its role in forming gap junction channels. Cx50 KO lenses exhibited increased intercellular spaces between lens fiber cells. The second extracellular loop domain (E2) is primarily responsible for this adhesive function. Treatment with a fusion protein containing E2 domain inhibited cell adhesion. Furthermore, disruption of cell adhesion by the E2 domains impaired primary lens cell differentiation. Five critical amino acid residues in the E2 domain primarily are involved in cell adhesive function as well as lens epithelial-fiber differentiation. Together, these results suggest that in addition to forming gap junction channels, Cx50 acts as an adhesive molecule that is critical in maintaining lens fiber integrity and epithelial-fiber differentiation.
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Affiliation(s)
- Zhengping Hu
- Departments of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Wen Shi
- Departments of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
- The Second Xiangya Hospital, Central South University, Changsha, China
| | - Manuel A Riquelme
- Departments of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Qian Shi
- Departments of Physiology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Sondip Biswas
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Woo-Kuen Lo
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA
| | - Sumin Gu
- Departments of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Jean X Jiang
- Departments of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA.
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14
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Rodriguez-Paris J, Waldhaus J, Gordhandas JA, Pique L, Schrijver I. Comparative functional characterization of novel non-syndromic GJB2 gene variant p.Gly45Arg and lethal syndromic variant p.Gly45Glu. PeerJ 2016; 4:e2494. [PMID: 27761313 PMCID: PMC5068369 DOI: 10.7717/peerj.2494] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 08/26/2016] [Indexed: 11/20/2022] Open
Abstract
We characterized a novel GJB2 missense variant, c.133G>A, p.Gly45Arg, and compared it with the only other variant at the same amino acid position of the connexin 26 protein (Cx26) reported to date: c.134G>A, p.Gly45Glu. Whereas both variants are associated with hearing loss and are dominantly inherited, p.Gly45Glu has been implicated in the rare fatal keratitis-ichthyosis-deafness (KID) syndrome, which results in cutaneous infections and septicemia with premature demise in the first year of life. In contrast, p.Gly45Arg appears to be non-syndromic. Subcellular localization experiments in transiently co-transfected HeLa cells demonstrated that Cx26-WT (wild-type) and p.Gly45Arg form gap junctions, whereas Cx26-WT with p.Gly45Glu protein does not. The substitution of a nonpolar amino acid glycine in wildtype Cx26 at position 45 with a negatively charged glutamic acid (acidic) has previously been shown to interfere with Ca2+ regulation of hemichannel gating and to inhibit the formation of gap junctions, resulting in cell death. The novel variant p.Gly45Arg, however, changes this glycine to a positively charged arginine (basic), resulting in the formation of dysfunctional gap junctions that selectively affect the permeation of negatively charged inositol 1,4,5-trisphosphate (IP3) and contribute to hearing loss. Cx26 p.Gly45Arg transfected cells, unlike cells transfected with p.Gly45Glu, thrived at physiologic Ca2+ concentrations, suggesting that Ca2+ regulation of hemichannel gating is unaffected in Cx26 p.Gly45Arg transfected cells. Thus, the two oppositely charged amino acids that replace the highly conserved uncharged glycine in p.Gly45Glu and p.Gly45Arg, respectively, produce strikingly different effects on the structure and function of the Cx26 protein.
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Affiliation(s)
- Juan Rodriguez-Paris
- Department of Pathology, Stanford University, Stanford, CA, United States of America
| | - Jörg Waldhaus
- Department of Otolaryngology, Head and Neck Surgery, Stanford University, Stanford, CA, United States of America
| | - Jeenal A Gordhandas
- Department of Pathology, Stanford University, Stanford, CA, United States of America
| | - Lynn Pique
- Department of Pathology, Stanford University, Stanford, CA, United States of America
| | - Iris Schrijver
- Department of Pathology, Stanford University, Stanford, CA, United States of America.,Department of Pediatrics, Stanford University, Stanford, CA, United States of America
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15
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Wang L, Chen Y, Chen X, Sun X. Further evidence for P59L mutation in GJA3 associated with autosomal dominant congenital cataract. Indian J Ophthalmol 2016; 64:508-12. [PMID: 27609163 PMCID: PMC5026076 DOI: 10.4103/0301-4738.190139] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 01/29/2016] [Indexed: 11/08/2022] Open
Abstract
CONTEXT Congenital cataracts are one of the common eye disorders leading to visual impairment or blindness in children worldwide. We found a Chinese family with autosomal dominant pulverulent cataract. AIMS To identify the pathogenic gene mutation in a Chinese family with autosomal dominant inherited pulverulent cataract. SUBJECTS AND METHODS After obtained informed consent, detailed ophthalmic examinations were carried out; genomic DNAs were obtained from seven family members in a three-generation Chinese family with three affected. All exons of candidate genes were amplified by polymerase chain reaction and were sequenced performed by bidirectional sequencing. RESULTS By sequencing the encoding regions of the candidate genes, a missense mutation (c. 176C>T) was detected in gap junction protein alpha 3 genes (GJA3), which resulted in the substitution of highly conserved proline by leucine at codon 59 (p.P59L). The mutation co-segregated with all patients and was absent in 100 normal Chinese controls. CONCLUSIONS The study identified a missense mutation (c. 176C>T) in GJA3 gene associated with autosomal dominant congenital pulverulent cataract in a Chinese family. It gave further evidence of phenotype heterogeneity for P59L mutation in GJA3 associated with congenital cataract.
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Affiliation(s)
- Li Wang
- Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China
- Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
- Key Laboratory of Myopia, Ministry of Health, Eye and ENT Hospital of Fudan University, Shanghai, China
| | - Yuhong Chen
- Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China
- Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
- Key Laboratory of Myopia, Ministry of Health, Eye and ENT Hospital of Fudan University, Shanghai, China
| | - Xueli Chen
- Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China
- Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
- Key Laboratory of Myopia, Ministry of Health, Eye and ENT Hospital of Fudan University, Shanghai, China
| | - Xinghuai Sun
- Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China
- Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
- Key Laboratory of Myopia, Ministry of Health, Eye and ENT Hospital of Fudan University, Shanghai, China
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16
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Dalamón VK, Buonfiglio P, Larralde M, Craig P, Lotersztein V, Choate K, Pallares N, Diamante V, Elgoyhen AB. Connexin 26 (GJB2) mutation in an Argentinean patient with keratitis-ichthyosis-deafness (KID) syndrome: a case report. BMC MEDICAL GENETICS 2016; 17:37. [PMID: 27141831 PMCID: PMC4855445 DOI: 10.1186/s12881-016-0298-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 04/22/2016] [Indexed: 11/20/2022]
Abstract
Background Keratitis-Ichthyosis-Deafness (KID) syndrome is a rare condition characterized by pre-lingual sensorineural deafness with skin hyperkeratinization. The primary cause of the disease is a loss-of-function mutation in the GJB2 gene. Mutations in Argentinean patients have not been described. Case presentation We studied a 2 year-old boy with bilateral congenital sensorineural deafness with dry skin over the entire body, hypotrichosis of the scalp, thin and light-blond hair. Analysis of the GJB2 gene nucleotide sequence revealed the substitution of guanine-148 by adenine predicted to result in an Asp50Asn amino acid substitution. Conclusion This is the first KID report in a patient from Argentina. This de novo mutation proved to be the cause of keratitis-ichthyosis-deafness syndrome (KID-syndrome) in the patient, and has implications in medical genetic practice.
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Affiliation(s)
- Viviana Karina Dalamón
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
| | - Paula Buonfiglio
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Margarita Larralde
- Servicio de Dermatología Pediátrica, Hospital Ramos Mejía, Ciudad Autonoma de Buenos Aires, Argentina.,Departamento de Dermatología, Hospital Alemán, Ciudad Autonoma de Buenos Aires, Argentina
| | - Patricio Craig
- Departamento de Química Biológica e Instituto de Química y Fisicoquímica Biológicas, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Ciudad Autonoma de Buenos Aires, Argentina
| | - Vanesa Lotersztein
- Servicio de Genética, Hospital de Clínicas "José de San Martín", Ciudad Autonoma de Buenos Aires, Argentina
| | - Keith Choate
- Dermatology Yale University School of Medicine, New Haven, USA
| | - Norma Pallares
- Instituto Superior de Implantes Cocleares "Dr. Vicente Diamante", Ciudad Autonoma de Buenos Aires, Argentina
| | - Vicente Diamante
- Instituto Superior de Implantes Cocleares "Dr. Vicente Diamante", Ciudad Autonoma de Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor Torres"-(INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Vuelta de Obligado 2490. (1428) Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.,Departamento de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Ciudad Autonoma de Buenos Aires, Argentina
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17
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Liu Y, Qiao C, Wei T, Zheng F, Guo S, Chen Q, Yan M, Zhou X. Mutant connexin 50 (S276F) inhibits channel and hemichannel functions inducing cataract. J Genet 2016; 94:221-9. [PMID: 26174669 DOI: 10.1007/s12041-015-0506-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This study was designed to detect the expression, detergent resistance, subcellular localization, and channel and hemichannel functions of mutant Cx50 to understand the forming mechanism for inducing congenital cataract by a novel mutation p.S276F in connexin 50 (Cx50) reported previously by us. HeLa and human lens epithelial (HLE) cells were transfected with wild-type Cx50 and mutant Cx50 (S276F). We examined the functional characteristics of mutant Cx50 (S276F) in comparison with those of wild-type Cx50 using immunoblot, confocal fluorescence microscopy, dye transfer analysis and dye uptake assay. The mutant and wild-type Cx50 were expressed in equal levels and could efficiently localize to the plasma membrane without transportation and assembly problems. Scrape loading dye transfer was significantly evident in cells transfected with wild-type Cx50 compared to those in cells transfected with mutant Cx50 and cotransfected with wild-type and mutant Cx50. The dye uptake was found to be significantly lower in cells transfected with mutant Cx50 than in cells transfected with wild- type Cx50 and cells cotransfected with wild-type and mutant Cx50. The transfected HeLa and HLE cell lines showed similar performance in all the experiments. These results indicated that the mutant Cx50 (S276F) might inhibit the function of gap junction channel in a dominant negative manner, but inhibit the hemichannel function in a recessive negative manner.
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Affiliation(s)
- Yuanyuan Liu
- Center for Gene Diagnosis, Zhongnan Hospital of Wuhan University, Donghu Road 169#, Wuhan, Hubei 430071, People's Republic of China.
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18
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The pathological effects of connexin 26 variants related to hearing loss by in silico and in vitro analysis. Hum Genet 2016; 135:287-98. [PMID: 26749107 DOI: 10.1007/s00439-015-1625-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 12/11/2015] [Indexed: 02/04/2023]
Abstract
Gap junctions (GJs) are intercellular channels associated with cell-cell communication. Connexin 26 (Cx26) encoded by the GJB2 gene forms GJs of the inner ear, and mutations of GJB2 cause congenital hearing loss that can be syndromic or non-syndromic. It is difficult to predict pathogenic effects using only genetic analysis. Using ionic and biochemical coupling tests, we evaluated the pathogenic effects of Cx26 variants using computational analyses to predict structural abnormalities. For seven out of ten variants, we predicted the variation would result in a loss of GJ function, whereas the others would completely fail to form GJs. Functional studies demonstrated that, although all variants were able to function normally as hetero-oligomeric GJ channels, six variants (p.E47K, p.E47Q, p.H100L, p.H100Y, p.R127L, and p.M195L) did not function normally as homo-oligomeric GJ channels. Interestingly, GJs composed of the Cx26 variant p.R127H were able to function normally, even as homo-oligomeric GJ channels. This study demonstrates the particular location and property of an amino acid are more important mainly than the domain where they belong in the formation and function of GJ, and will provide information that is useful for the accurate diagnosis of hearing loss.
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19
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Lee JY, Choi EJ, Lee J. A new high-throughput screening-compatible gap junctional intercellular communication assay. BMC Biotechnol 2015; 15:90. [PMID: 26444544 PMCID: PMC4596302 DOI: 10.1186/s12896-015-0211-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Accepted: 10/01/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Gap junctions (GJs) are intercellular channels through which molecules smaller than 1 kDa can diffuse, and they have been suggested as drug targets. To develop chemical drugs acting on this target, a high-throughput screening (HTS) system for GJ modulators is necessary. RESULTS We designed a new, high-throughput GJ intercellular communication (GJIC) assay. This assay system consisted of donor and acceptor cells from LN215 glioma cells that expressed SLC26A4 and yellow fluorescent protein-H148Q/I152L (YFP(QL)), respectively. The fluorescence of LN215-YFP(QL) acceptor cells, when cultured alone, was not quenched by iodide. However when donor and acceptor cells, or LN215-YFP(QL) and LN215-I(-) cells, were mixed and plated, they formed GJs. When iodide was added, it was transported into donor cells by SLC26A4, diffused through the GJs to acceptor cells, and quenched the YFP(QL) fluorescence. The quenching rate was optimal at a 2:1 mixture of donor and acceptor cells. The assay quality parameter, Z' factor, was calculated from data collected with vehicle and carbenoxolone. For each assay, the Z' factor increased with time. The Z' factor of a 10-s assay was 0.72 indicating that the assay quality was high enough for use in HTS. This assay system also worked well in HOS osteosarcoma cells with a Z' factor at 10 s of 0.70. CONCLUSIONS We developed a new HTS system for GJ modulators. The system had a high assay quality with a Z' factor ≥ 0.70, was rapid and required only 10 s per well, was inexpensive in requiring no additional reagents, and was predicted to have a low rate of false-positive hits.
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Affiliation(s)
- Ju Yeon Lee
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, 85 Songdogwahak-ro, Yeonsu-gu, Incheon, 406-840, South Korea.
| | - Eun Ju Choi
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, 85 Songdogwahak-ro, Yeonsu-gu, Incheon, 406-840, South Korea.
| | - Jinu Lee
- College of Pharmacy, Yonsei Institute of Pharmaceutical Sciences, Yonsei University, 85 Songdogwahak-ro, Yeonsu-gu, Incheon, 406-840, South Korea.
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20
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Pelletier RM, Akpovi CD, Chen L, Kumar NM, Vitale ML. Complementary expression and phosphorylation of Cx46 and Cx50 during development and following gene deletion in mouse and in normal and orchitic mink testes. Am J Physiol Regul Integr Comp Physiol 2015; 309:R255-76. [PMID: 26017495 PMCID: PMC4525330 DOI: 10.1152/ajpregu.00152.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 05/23/2015] [Indexed: 01/11/2023]
Abstract
Gap junction-mediated communication helps synchronize interconnected Sertoli cell activities. Besides, coordination of germ cell and Sertoli cell activities depends on gap junction-mediated Sertoli cell-germ cell communication. This report assesses mechanisms underlying the regulation of connexin 46 (Cx46) and Cx50 in mouse testis and those accompanying a "natural" seasonal and a pathological arrest of spermatogenesis, resulting from autoimmune orchitis (AIO) in mink. Furthermore, the impact of deleting Cx46 or Cx50 on the expression, phosphorylation of junction proteins, and spermatogenesis is evaluated. Cx46 mRNA and protein expression increased, whereas Cx50 decreased with adulthood in normal mice and mink. Cx46 mRNA and protein expression increased, whereas Cx50 decreased with adulthood in normal mice and mink. During the mink active spermatogenic phase, Cx50 became phosphorylated and localized to the site of the blood-testis barrier. By contrast, Cx46 was dephosphorylated and associated with annular junctions, suggesting phosphorylation/dephosphorylation of Cx46 and Cx50 involvement in the barrier dynamics. Cx46-positive annular junctions in contact with lipid droplets were found. Cx46 and Cx50 expression and localization were altered in mink with AIO. The deletion of Cx46 or Cx50 impacted on other connexin expression and phosphorylation and differently affected tight and adhering junction protein expression. The level of apoptosis, determined by ELISA, and a number of Apostain-labeled spermatocytes and spermatids/tubules were higher in mice lacking Cx46 (Cx46-/-) than wild-type and Cx50-/- mice, arguing for life-sustaining Cx46 gap junction-mediated exchanges in late-stage germ cells secluded from the blood by the barrier. The data show that expression and phosphorylation of Cx46 and Cx50 are complementary in seminiferous tubules.
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Affiliation(s)
- R-Marc Pelletier
- Department of Pathology and Cell Biology, Université de Montréal, Québec, Canada; and
| | - Casimir D Akpovi
- Department of Pathology and Cell Biology, Université de Montréal, Québec, Canada; and
| | - Li Chen
- Department of Pathology and Cell Biology, Université de Montréal, Québec, Canada; and
| | - Nalin M Kumar
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - María L Vitale
- Department of Pathology and Cell Biology, Université de Montréal, Québec, Canada; and
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21
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M Kidder G, Winterhager E. Physiological roles of connexins in labour and lactation. Reproduction 2015; 150:R129-36. [PMID: 26150552 DOI: 10.1530/rep-15-0134] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 07/06/2015] [Indexed: 01/08/2023]
Abstract
The connexin family of proteins are best known as oligomerizing to form intercellular membrane channels (gap junctions) that metabolically and ionically couple cells to allow for coordinated cellular function. Nowhere in the body is this role better illustrated than in the uterine smooth muscle during parturition, where gap junctions conduct the contraction wave throughout the tissue to deliver the baby. Parturition is followed by the onset of lactation with connexins contributing to both the dramatic reorganization of mammary gland tissue leading up to lactation and the smooth muscle contraction of the myoepithelial cells which extrudes the milk. This review summarizes what is known about the expression and roles of individual connexin family members in the uterus during labour and in the mammary glands during development and lactation. Connexin loss or malfunction in mammary glands and the uterus can have serious implications for the health of both the mother and the newborn baby.
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Affiliation(s)
- Gerald M Kidder
- Department of Physiology and PharmacologySchulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario N6A 5C1, CanadaInstitute of Molecular BiologyUniversity of Duisburg-Essen, University Clinics, 45211 Essen, Germany
| | - Elke Winterhager
- Department of Physiology and PharmacologySchulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario N6A 5C1, CanadaInstitute of Molecular BiologyUniversity of Duisburg-Essen, University Clinics, 45211 Essen, Germany
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22
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Yao F, Yue M, Zhang C, Zuo X, Zheng X, Zhang A, Wang Z, Liu S, Li H, Meng L, Zeng M, Fan X, Sun L, Zhang X. A genetic coding variant rs72474224 in GJB2 is associated with clinical features of psoriasis vulgaris in a Chinese Han population. ACTA ACUST UNITED AC 2015; 86:134-8. [PMID: 26104599 DOI: 10.1111/tan.12595] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 04/22/2015] [Accepted: 05/22/2015] [Indexed: 12/19/2022]
Abstract
Our recent targeted sequencing study identified a missense single-nucleotide polymorphism rs72474224 (c.324C>T) in GJB2. To investigate the correlation between rs72474224 (c.324C>T) and subphenotypes of psoriasis, genotype data for rs72474224 (c.324C>T, p.Val37Ile) was analyzed in 9946 cases and 9906 controls. The additive model provided the best fit for rs72474224 (P = 7.34 × 10(-9)). The genotypic and allelic frequency distributions were associated with plaque psoriasis in case-only (Pgenotype = 2.67 × 10(-3), Pallele = 6.22 × 10(-4)) and subphenotype-control (Pgenotype = 1.58 × 10(-11), Pallele = 8.16 × 10(-12)) analyses. No other significant difference was found in case-only analyses. Rs72474224 in GJB2 is preferentially associated with plaque psoriasis in Chinese population and might contribute to the complexity of psoriasis clinical features.
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Affiliation(s)
- F Yao
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China.,Department of Dermatology at Anqing Hospital, Anhui Medical University, Hefei, China
| | - M Yue
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - C Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zuo
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zheng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - A Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - Z Wang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - S Liu
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - H Li
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Meng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - M Zeng
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Fan
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - L Sun
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
| | - X Zhang
- Institute of Dermatology and Department of Dermatology, Anhui Medical University, Hefei, China.,State Key Laboratory Incubation Base of Dermatology, Anhui Medical University, Hefei, China
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Degradation of gap junction connexins is regulated by the interaction with Cx43-interacting protein of 75 kDa (CIP75). Biochem J 2015; 466:571-85. [PMID: 25583071 DOI: 10.1042/bj20141042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Connexins are a family of transmembrane proteins that form gap junction channels. These proteins undergo both proteasomal and lysosomal degradation, mechanisms that serve to regulate connexin levels. Our previous work described CIP75 [connexin43 (Cx43)-interacting protein of 75 kDa], a protein involved in proteasomal degradation, as a novel Cx43-interacting protein. We have discovered two additional connexins, connexin40 (Cx40) and connexin45 (Cx45), that interact with CIP75. Nuclear magnetic resonance (NMR) analyses identified the direct interaction of the CIP75 UBA domain with the carboxyl-terminal (CT) domains of Cx40 and Cx45. Reduction in CIP75 by shRNA in HeLa cells expressing Cx40 or Cx45 resulted in increased levels of the connexins. Furthermore, treatment with trafficking inhibitors confirmed that both connexins undergo endoplasmic reticulum-associated degradation (ERAD), and that CIP75 preferentially interacts with the connexin proteins bound for proteasomal degradation from the ER. In addition, we have also discovered that CIP75 interacts with ER-localized Cx32 in a process that is likely mediated by Cx32 ubiquitination. Thus, we have identified novel interacting connexin proteins of CIP75, indicating a role for CIP75 in regulating the levels of connexins in general, through proteasomal degradation.
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Nishii K, Shibata Y, Kobayashi Y. Connexin mutant embryonic stem cells and human diseases. World J Stem Cells 2014; 6:571-578. [PMID: 25426253 PMCID: PMC4178256 DOI: 10.4252/wjsc.v6.i5.571] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 09/11/2014] [Accepted: 09/17/2014] [Indexed: 02/06/2023] Open
Abstract
Intercellular communication via gap junctions allows cells within multicellular organisms to share small molecules. The effect of such interactions has been elucidated using mouse gene knockout strategies. Although several mutations in human gap junction-encoding connexin (Cx) have been described, Cx mutants in mice do not always recapitulate the human disease. Among the 20 mouse Cxs, Cx26, Cx43, and Cx45 play roles in early cardiac or placental development, and disruption of the genes results in lethality that hampers further analyses. Embryonic stem cells (ESCs) that lack Cx43 or Cx45 have made analysis feasible in both in vitro differentiated cell cultures and in vivo chimeric tissues. The success of mouse ESCs studies is leading to the use of induced pluripotent stem cells to learn more about the pathogenesis of human Cx diseases. This review summarizes the current status of mouse Cx disruption models and ESC differentiation studies, and discusses their implication for understanding human Cx diseases.
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25
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Le Gal L, Alonso F, Wagner C, Germain S, Nardelli Haefliger D, Meda P, Haefliger JA. Restoration of connexin 40 (Cx40) in Renin-producing cells reduces the hypertension of Cx40 null mice. Hypertension 2014; 63:1198-204. [PMID: 24614215 DOI: 10.1161/hypertensionaha.113.02976] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Connexin 40 (Cx40) is expressed by the renin-producing cells (RSCs) of the kidneys and the endothelial cells of blood vessels. Cx40 null mice (Cx40(-/-)) feature a much increased renin synthesis and secretion, which results in chronic hypertension, and also display an altered endothelium-dependent relaxation of the aorta because of reduced eNOS levels and nitric oxide production. To discriminate the effect of Cx40 in renin secretion and vascular signaling, we targeted Cx40 to either the RSCs or the endothelial cells of Cx40 null mice. When compared with Cx40(-/-) controls, the animals expressing Cx40 in RSCs were less hypertensive and featured reduced renin levels, still numerous RSCs outside the wall of the afferent arterioles. In contrast, mice expressing Cx40 in the endothelial cells were as hypertensive as Cx40(-/-) mice, in spite of control levels of Cx37 and eNOS. Our data show that blood pressure is improved by restoration of Cx40 expression in RSCs but not in endothelial cells, stressing the prominent role of renin in the mouse hypertension linked to loss of Cx40.
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Affiliation(s)
- Loïc Le Gal
- Department of Medicine, Laboratory of Experimental Medicine, c/o Department of Physiology, Bugnon 7a, 1005 Lausanne, Switzerland.
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26
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Fiori MC, Reuss L, Cuello LG, Altenberg GA. Functional analysis and regulation of purified connexin hemichannels. Front Physiol 2014; 5:71. [PMID: 24611052 PMCID: PMC3933781 DOI: 10.3389/fphys.2014.00071] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 02/06/2014] [Indexed: 01/08/2023] Open
Abstract
Gap-junction channels (GJCs) are aqueous channels that communicate adjacent cells. They are formed by head-to-head association of two hemichannels (HCs), one from each of the adjacent cells. Functional HCs are connexin hexamers composed of one or more connexin isoforms. Deafness is the most frequent sensineural disorder, and mutations of Cx26 are the most common cause of genetic deafness. Cx43 is the most ubiquitous connexin, expressed in many organs, tissues, and cell types, including heart, brain, and kidney. Alterations in its expression and function play important roles in the pathophysiology of very frequent medical problems such as those related to cardiac and brain ischemia. There is extensive information on the relationship between phosphorylation and Cx43 targeting, location, and function from experiments in cells and organs in normal and pathological conditions. However, the molecular mechanisms of Cx43 regulation by phosphorylation are hard to tackle in complex systems. Here, we present the use of purified HCs as a model for functional and structural studies. Cx26 and Cx43 are the only isoforms that have been purified, reconstituted, and subjected to functional and structural analysis. Purified Cx26 and Cx43 HCs have properties compatible with those demonstrated in cells, and present methodologies for the functional analysis of purified HCs reconstituted in liposomes. We show that phosphorylation of serine 368 by PKC produces a partial closure of the Cx43 HCs, changing solute selectivity. We also present evidence that the effect of phosphorylation is highly cooperative, requiring modification of several connexin subunits, and that phosphorylation of serine 368 elicits conformational changes in the purified HCs. The use of purified HCs is starting to provide critical data to understand the regulation of HCs at the molecular level.
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Affiliation(s)
- Mariana C Fiori
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center Lubbock, TX, USA
| | - Luis Reuss
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center Lubbock, TX, USA
| | - Luis G Cuello
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center Lubbock, TX, USA
| | - Guillermo A Altenberg
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center Lubbock, TX, USA
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27
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Syndromic and non-syndromic disease-linked Cx43 mutations. FEBS Lett 2014; 588:1339-48. [PMID: 24434540 DOI: 10.1016/j.febslet.2013.12.022] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 12/30/2013] [Indexed: 01/05/2023]
Abstract
There are now at least 14 distinct diseases linked to germ line mutations in the 21 genes that encode the connexin (Cx) family of gap junction proteins. This review focuses on the links between germ-line mutations in the gene encoding Cx43 (GJA1) and the human disease termed oculodentodigital dysplasia (ODDD). This disease is clinically characterized by soft tissue fusion of the digits, abnormal craniofacial bone development, small eyes and loss of tooth enamel. However, the disease is considerably more complex and somewhat degenerative as patients often suffer from other syndromic effects that include incontinence, glaucoma, skin diseases and neuropathies that become more pronounced during aging. The challenge continues to be understanding how distinct Cx43 gene mutations cause such a diverse range of tissue phenotypes and pathophysiological changes while other Cx43-rich organs are relatively unaffected. This review will provide an overview of many of these studies and distill some themes and outstanding questions that need to be addressed in the coming years.
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28
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Ambrosi C, Walker AE, DePriest AD, Cone AC, Lu C, Badger J, Skerrett IM, Sosinsky GE. Analysis of trafficking, stability and function of human connexin 26 gap junction channels with deafness-causing mutations in the fourth transmembrane helix. PLoS One 2013; 8:e70916. [PMID: 23967136 PMCID: PMC3744544 DOI: 10.1371/journal.pone.0070916] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 06/25/2013] [Indexed: 01/24/2023] Open
Abstract
Human Connexin26 gene mutations cause hearing loss. These hereditary mutations are the leading cause of childhood deafness worldwide. Mutations in gap junction proteins (connexins) can impair intercellular communication by eliminating protein synthesis, mis-trafficking, or inducing channels that fail to dock or have aberrant function. We previously identified a new class of mutants that form non-functional gap junction channels and hemichannels (connexons) by disrupting packing and inter-helix interactions. Here we analyzed fourteen point mutations in the fourth transmembrane helix of connexin26 (Cx26) that cause non-syndromic hearing loss. Eight mutations caused mis-trafficking (K188R, F191L, V198M, S199F, G200R, I203K, L205P, T208P). Of the remaining six that formed gap junctions in mammalian cells, M195T and A197S formed stable hemichannels after isolation with a baculovirus/Sf9 protein purification system, while C202F, I203T, L205V and N206S formed hemichannels with varying degrees of instability. The function of all six gap junction-forming mutants was further assessed through measurement of dye coupling in mammalian cells and junctional conductance in paired Xenopus oocytes. Dye coupling between cell pairs was reduced by varying degrees for all six mutants. In homotypic oocyte pairings, only A197S induced measurable conductance. In heterotypic pairings with wild-type Cx26, five of the six mutants formed functional gap junction channels, albeit with reduced efficiency. None of the mutants displayed significant alterations in sensitivity to transjunctional voltage or induced conductive hemichannels in single oocytes. Intra-hemichannel interactions between mutant and wild-type proteins were assessed in rescue experiments using baculovirus expression in Sf9 insect cells. Of the four unstable mutations (C202F, I203T, L205V, N206S) only C202F and N206S formed stable hemichannels when co-expressed with wild-type Cx26. Stable M195T hemichannels displayed an increased tendency to aggregate. Thus, mutations in TM4 cause a range of phenotypes of dysfunctional gap junction channels that are discussed within the context of the X-ray crystallographic structure.
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Affiliation(s)
- Cinzia Ambrosi
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, California, United States of America
| | - Amy E. Walker
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, California, United States of America
| | - Adam D. DePriest
- Biology Department, State University of New York Buffalo State, Buffalo, New York, United States of America
| | - Angela C. Cone
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, California, United States of America
| | - Connie Lu
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, California, United States of America
| | - John Badger
- DeltaG Technologies, San Diego, California, United States of America
| | - I. Martha Skerrett
- Biology Department, State University of New York Buffalo State, Buffalo, New York, United States of America
| | - Gina E. Sosinsky
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California San Diego, La Jolla, California, United States of America
- Department of Neurosciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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29
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Zhao X, Xu F, Tang L, Du W, Feng X, Liu BF. Microfluidic chip-based C. elegans microinjection system for investigating cell-cell communication in vivo. Biosens Bioelectron 2013; 50:28-34. [PMID: 23831644 DOI: 10.1016/j.bios.2013.06.024] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 06/09/2013] [Accepted: 06/10/2013] [Indexed: 11/30/2022]
Abstract
The propagation of intercellular calcium wave (ICW) is essential for coordinating cellular activities in multicellular organisms. However, the limitations of existing analytical methods hamper the studies of this biological process in live animals. In this paper, we demonstrated for the first time a novel microfluidic system with an open chamber for on-chip microinjection of C. elegans and investigation of ICW propagations in vivo. Worms were long-term immobilized on the side wall of the open chamber by suction. Using an external micro-manipulator, localized chemical stimulation was delivered to single intestinal cells of the immobilized worms by microinjection. The calcium dynamics in the intestinal cells expressing Ca(2+) indicator YC2.12 was simultaneously monitored by fluorescence imaging. As a result, thapsigargin injection induced ICW was observed in the intestinal cells of C. elegans. Further analysis of the ICW propagation was realized in the presence of heparin (an inhibitor for IP3 receptor), which allowed us to investigate the mechanism underlying intercellular calcium signaling. We expect this novel microfluidic platform to be a useful tool for studying cell-cell communication in multicellular organisms in vivo.
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Affiliation(s)
- Xingfu Zhao
- Britton Chance Center for Biomedical Photonics at Wuhan National Laboratory for Optoelectronics-Hubei Bioinformatics & Molecular Imaging Key Laboratory, Systems Biology Theme, Department of Biomedical Engineering, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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30
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Su D, Yang Z, Li Q, Guan L, Zhang H, E D, Zhang L, Zhu S, Ma X. Identification and functional analysis of GJA8 mutation in a Chinese family with autosomal dominant perinuclear cataracts. PLoS One 2013; 8:e59926. [PMID: 23555834 PMCID: PMC3612055 DOI: 10.1371/journal.pone.0059926] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/20/2013] [Indexed: 11/25/2022] Open
Abstract
Congenital cataract is a clinically and genetically heterogeneous group of eye disorders that causes visual impairment and childhood blindness. The purpose of this study was to identify the genetic defect associated with autosomal dominant congenital perinuclear cataract in a Chinese family. A detailed family history and clinical data of the family were recorded, and candidate gene sequencing was performed to screen for mutation-causing disease in our study. Direct sequencing revealed a c.601G>A (p.E201K) transversion in exon 2 of GJA8. This mutation co-segregated with all affected individuals in the family and was not found in unaffected family members or 100 unrelated controls. The function and mechanism of novel GJA8 point mutation E201K in Chinese patients were then investigated in this study. We found E201K aberrantly located in cytoplasm and prevented its location in the plasma membrane. Induction of E201K expression led to a decrease in cell growth and viability by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Our study provides important evidence that GJA8 is a disease-causing gene for congenital cataract and that mutation of GJA8 has a potential causative effect.
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Affiliation(s)
- Dongmei Su
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Zhenfei Yang
- Capital Medical University,Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Qian Li
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Lina Guan
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Huiling Zhang
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Dandan E
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Lei Zhang
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
| | - Siquan Zhu
- Capital Medical University,Beijing Ophthalmology and Visual Sciences Key Lab, Beijing, China
| | - Xu Ma
- Department of Genetics, National Research Institute for Family Planning, Beiing, China
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31
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Zonta F, Polles G, Zanotti G, Mammano F. Permeation pathway of homomeric connexin 26 and connexin 30 channels investigated by molecular dynamics. J Biomol Struct Dyn 2012; 29:985-98. [PMID: 22292956 DOI: 10.1080/073911012010525027] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mutations in the genes GJB2 and GJB6 encoding human connnexin26 (hCx26) and connexin30 (hCx30), respectively, are the leading cause of non-syndromic prelingual deafness in several human populations. In this work, we exploited the high degree (77%) of sequence similarity shared by hCx26 and hCx30 to create atomistic models of homomeric hCx26 and hCx30 connexons starting from the X-ray crystallographic structure of an intercellular channel formed by hCx26 protomers at 3.5-å resolution. The equilibrium dynamics of the two protein complexes was followed for 40 ns each by Molecular Dynamics (MD) simulations. Our results indicate that, in hCx26, positively charged Lys41 residues establish a potential barrier within the fully open channel, hindering ion diffusion in the absence of an electrochemical gradient. A similar role is played, in hCx30, by negatively charged Glu49 residues. The different position and charge of these two ion sieves account for the differences in unitary conductance observed experimentally. Our results are discussed in terms of present models of voltage gating in connexin channels.
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Affiliation(s)
- Francesco Zonta
- Department of Physics and Astronomy G.Galilei, University of Padua, 35129 Padua, Italy
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32
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Chen P, Chen P, Feng X, Du W, Liu BF. Analysis of intercellular communication by flexible hydrodynamic gating on a microfluidic chip. Anal Bioanal Chem 2012; 405:307-14. [PMID: 23052886 DOI: 10.1007/s00216-012-6447-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 08/31/2012] [Accepted: 09/21/2012] [Indexed: 01/09/2023]
Abstract
Intercellular Ca(2+) waves are propagation of Ca(2+) transients among cells that could be initiated by chemical stimulation. Current methods for analyzing intercellular Ca(2+) waves are difficult to realize localized chemical stimulations upon the target cell without interfering with adjacent contacting cells. In this paper, a simple and flexible microfluidic method was developed for investigating the intercellular communication of Ca(2+) signals. A cross-patterned microfluidic chip was designed and fabricated with polydimethylsiloxane as the structural material. Localized chemical stimulation was achieved by a new strategy based on hydrodynamic gating technique. Clusters of target cells were seeded at the location within 300 μm downstream of the intersection of the cross-shaped microchannel. Confined lateral molecular diffusion largely minimized the interference from diffusion-induced stimulation of adjacent cells. Localized stimulation of the target cell with adenosine 5'-triphosphate successfully induced the propagation of intercellular Ca(2+) waves among a population of adjacent contacting cells. Further inhibition studies verified that the propagation of calcium signals among NIH-3 T3 cells was dependent on direct cytosolic transfer via gap junctions. The developed microfluidic method provides a versatile platform for investigating the dynamics of intercellular communications.
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Affiliation(s)
- Peng Chen
- Britton Chance Center for Biomedical Photonics at Wuhan National Laboratory for Optoelectronics-Hubei Bioinformatics, Systems Biology Theme, Department of Biomedical Engineering, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
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33
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Schlingmann B, Schadzek P, Busko S, Heisterkamp A, Ngezahayo A. Cataract-associated D3Y mutation of human connexin46 (hCx46) increases the dye coupling of gap junction channels and suppresses the voltage sensitivity of hemichannels. J Bioenerg Biomembr 2012; 44:607-14. [PMID: 22843197 DOI: 10.1007/s10863-012-9461-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 07/08/2012] [Indexed: 10/28/2022]
Abstract
Connexin46 (Cx46), together with Cx50, forms gap junction channels between lens fibers and participates in the lens pump-leak system, which is essential for the homeostasis of this avascular organ. Mutations in Cx50 and Cx46 correlate with cataracts, but the functional relationship between the mutations and cataract formation is not always clear. Recently, it was found that a mutation at the third position of hCx46 that substituted an aspartic acid residue with a tyrosine residue (hCx46D3Y) caused an autosomal dominant zonular pulverulent cataract. We expressed EGFP-labeled hCx46wt and hCx46D3Y in HeLa cells and found that the mutation did not affect the formation of gap junction plaques. Dye transfer experiments using Lucifer Yellow (LY) and ethidium bromide (EthBr) showed an increased degree of dye coupling between the cell pairs expressing hCx46D3Y in comparison to the cell pairs expressing hCx46wt. In Xenopus oocytes, two-electrode voltage-clamp experiments revealed that hCx46wt formed voltage-sensitive hemichannels. This was not observed in the oocytes expressing hCx46D3Y. The replacement of the aspartic acid residue at the third position by another negatively charged residue, glutamic acid, to generate the mutant hCx46D3E, restored the voltage sensitivity of the resultant hemichannels. Moreover, HeLa cell pairs expressing hCx46D3E and hCx46wt showed a similar degree of dye coupling. These results indicate that the negatively charged aspartic acid residue at the third position of the N-terminus of hCx46 could be involved in the determination of the degree of metabolite cell-to-cell coupling and is essential for the voltage sensitivity of the hCx46 hemichannels.
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34
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Liu QP, Wu LS, Li FF, Liu S, Su J, Kuang YH, Chen C, Xie XY, Jiang MH, Zhao S, Chen ML, Chen X. The association between GJB2 gene polymorphism and psoriasis: a verification study. Arch Dermatol Res 2012; 304:769-72. [PMID: 22890607 DOI: 10.1007/s00403-012-1273-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 07/16/2012] [Accepted: 07/19/2012] [Indexed: 12/31/2022]
Abstract
Psoriasis is a chronic inflammatory skin disease with multifactorial etiology. Connexin 26 (Cx26), an important gap junction protein, has been found highly expressed in plaques of psoriasis. Recently, genome wide association studies (GWAS) identified one new single nucleotide polymorphism (SNP) in GJB2 gene coding for Cx26 protein associated with psoriasis in Chinese Han population. In this paper, we verified the GWAS data in Chinese Han population. Here we genotyped the polymorphism of GJB2 rs3751385:C>T in 371 psoriasis patients and 330 healthy controls in Chinese Han population using polymerase chain reaction restriction fragment length polymorphism assay (PCR-RFLP). Our case-control assay indicated decreased frequency of the GJB2 rs3751385 C allele in psoriasis patients compared with that in the healthy controls [p = 6.02 × 10(-5), Odds ratio (OR) = 0.793, 95 % confidence interval (CI) 0.706-0.889]. The result suggested that GJB2 gene polymorphism rs3751385:C>T was associated with psoriasis susceptibility of Chinese Han population.
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Affiliation(s)
- Que-Ping Liu
- Department of Dermatology, Xiang-Ya Hospital Central South University, Changsha, Hunan, People's Republic of China
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35
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Carvalho CPF, Oliveira RB, Britan A, Santos-Silva JC, Boschero AC, Meda P, Collares-Buzato CB. Impaired β-cell-β-cell coupling mediated by Cx36 gap junctions in prediabetic mice. Am J Physiol Endocrinol Metab 2012; 303:E144-51. [PMID: 22569071 DOI: 10.1152/ajpendo.00489.2011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Gap junctional intercellular communication between β-cells is crucial for proper insulin biosynthesis and secretion. The aim of this work was to investigate the expression of connexin (Cx)36 at the protein level as well as the function and structure of gap junctions (GJ) made by this protein in the endocrine pancreas of prediabetic mice. C57BL/6 mice were fed a high-fat (HF) or regular chow diet for 60 days. HF-fed mice became obese and prediabetic, as shown by peripheral insulin resistance, moderate hyperglycemia, hyperinsulinemia, and compensatory increase in endocrine pancreas mass. Compared with control mice, prediabetic animals showed a significant decrease in insulin-secretory response to glucose and displayed a significant reduction in islet Cx36 protein. Ultrastructural analysis further showed that prediabetic mice had GJ plaques about one-half the size of those of the control group. Microinjection of isolated pancreatic islets with ethidium bromide revealed that prediabetic mice featured a β-cell-β-cell coupling 30% lower than that of control animals. We conclude that β-cell-β-cell coupling mediated by Cx36 made-channels is impaired in prediabetic mice, suggesting a role of Cx36-dependent cell-to-cell communication in the pathogenesis of the early β-cell dysfunctions that lead to type 2-diabetes.
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Affiliation(s)
- C P F Carvalho
- Department of Histology and Embryology, Institute of Biology, University of Campinas, Campinas, São Paulo, Brazil
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36
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Gerhart SV, Eble DM, Burger RM, Oline SN, Vacaru A, Sadler KC, Jefferis R, Iovine MK. The Cx43-like connexin protein Cx40.8 is differentially localized during fin ontogeny and fin regeneration. PLoS One 2012; 7:e31364. [PMID: 22347467 PMCID: PMC3275562 DOI: 10.1371/journal.pone.0031364] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Accepted: 01/09/2012] [Indexed: 11/18/2022] Open
Abstract
Connexins (Cx) are the subunits of gap junctions, membraneous protein channels that permit the exchange of small molecules between adjacent cells. Cx43 is required for cell proliferation in the zebrafish caudal fin. Previously, we found that a Cx43-like connexin, cx40.8, is co-expressed with cx43 in the population of proliferating cells during fin regeneration. Here we demonstrate that Cx40.8 exhibits novel differential subcellular localization in vivo, depending on the growth status of the fin. During fin ontogeny, Cx40.8 is found at the plasma membrane, but Cx40.8 is retained in the Golgi apparatus during regeneration. We next identified a 30 amino acid domain of Cx40.8 responsible for its dynamic localization. One possible explanation for the differential localization is that Cx40.8 contributes to the regulation of Cx43 in vivo, perhaps modifying channel activity during ontogenetic growth. However, we find that the voltage-gating properties of Cx40.8 are similar to Cx43. Together our findings reveal that Cx40.8 exhibits differential subcellular localization in vivo, dependent on a discrete domain in its carboxy terminus. We suggest that the dynamic localization of Cx40.8 differentially influences Cx43-dependent cell proliferation during ontogeny and regeneration.
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Affiliation(s)
- Sarah V. Gerhart
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Diane M. Eble
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - R. Michael Burger
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Stefan N. Oline
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Ana Vacaru
- Department of Medicine-Division of Liver Disease, Department of Regenerative and Developmental Biology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Kirsten C. Sadler
- Department of Medicine-Division of Liver Disease, Department of Regenerative and Developmental Biology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Rebecca Jefferis
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - M. Kathryn Iovine
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
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37
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Sun J, Zheng Y, Feng X, Du W, Liu BF. Analysis of intercellular calcium signaling using microfluidic adjustable laminar flow for localized chemical stimulation. Anal Chim Acta 2012; 721:104-9. [PMID: 22405307 DOI: 10.1016/j.aca.2012.01.053] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 01/20/2012] [Accepted: 01/26/2012] [Indexed: 01/09/2023]
Abstract
The propagation of intercellular calcium signals provides a mechanism to coordinate cell population activity, which is essential for regulating cell behavior and organ development. However, existing analytical methods are difficult to realize localized chemical stimulation of a single cell among a population of cells that are in close contact with one another for studying the propagation of calcium wave. In this work, a microfluidic method is presented for the analysis of contact-dependent propagation of intercellular calcium wave induced by extracellular ATP using multiple laminar flows. Adjacent cells were seeded ∼300 μm downstream the intersection of a Y-shaped microchannel with negative pressure pulses. Consequently, the lateral diffusion distance of the chemical at cell locations was limited to ∼26 μm with a total flow rate of 20 μL min(-1), which prevented the interference of diffusion-induced cellular responses. Localized stimulation of the target cell with ATP induced the propagation of intercellular calcium wave among the cell population. In addition, studies on the spread of intercellular calcium wave under octanol inhibition allowed us to characterize the gap junction mediated cell-cell communication. Thus, this novel device will provide a versatile platform for intercellular signal transduction studies and high throughput drug screening.
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Affiliation(s)
- Jian Sun
- Britton Chance Center for Biomedical Photonics at Wuhan National Laboratory for Optoelectronics-Hubei Bioinformatics, Department of Systems Biology, College of Life Science and Technology, Huazhong University of Science and Technology, People's Republic of China
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38
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Yan X, Zhang T, Wang Z, Jiang Y, Chen Y, Wang H, Ma D, Wang L, Li H. A novel mutation in the MITF may be digenic with GJB2 mutations in a large Chinese family of Waardenburg syndrome type II. J Genet Genomics 2011; 38:585-91. [DOI: 10.1016/j.jgg.2011.11.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 11/06/2011] [Accepted: 11/15/2011] [Indexed: 11/24/2022]
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39
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Zhao W, Han HB, Zhang ZQ. Suppression of lung cancer cell invasion and metastasis by connexin43 involves the secretion of follistatin-like 1 mediated via histone acetylation. Int J Biochem Cell Biol 2011; 43:1459-68. [DOI: 10.1016/j.biocel.2011.06.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Revised: 05/28/2011] [Accepted: 06/14/2011] [Indexed: 11/30/2022]
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40
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Pathological hemichannels associated with human Cx26 mutations causing Keratitis-Ichthyosis-Deafness syndrome. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:2014-9. [PMID: 21933663 DOI: 10.1016/j.bbamem.2011.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Revised: 08/30/2011] [Accepted: 09/06/2011] [Indexed: 12/25/2022]
Abstract
Connexin (Cx) proteins form intercellular gap junction channels by first assembling into single membrane hemichannels that then dock to connect the cytoplasm of two adjacent cells. Gap junctions are highly specialized structures that allow the direct passage of small molecules between cells to maintain tissue homeostasis. Functional activity of nonjunctional hemichannels has now been shown in several experimental systems. Hemichannels may constitute an important diffusional exchange pathway with the extracellular space, but the extent of their normal physiological role is currently unknown. Aberrant hemichannel activity has been linked to mutations of connexin proteins involved in genetic diseases. Here, we review a proposed role for hemichannels in the pathogenesis of Keratitis-Ichthyosis-Deafness (KID) syndrome associated with connexin26 (Cx26) mutations. Continued functional evaluation of mutated hemichannels linked to human hereditary disorders may provide additional insights into the mechanisms governing their regulation in normal physiology and dysregulation in disease. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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41
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Dahm R, van Marle J, Quinlan RA, Prescott AR, Vrensen GFJM. Homeostasis in the vertebrate lens: mechanisms of solute exchange. Philos Trans R Soc Lond B Biol Sci 2011; 366:1265-77. [PMID: 21402585 DOI: 10.1098/rstb.2010.0299] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The eye lens is avascular, deriving nutrients from the aqueous and vitreous humours. It is, however, unclear which mechanisms mediate the transfer of solutes between these humours and the lens' fibre cells (FCs). In this review, we integrate the published data with the previously unpublished ultrastructural, dye loading and magnetic resonance imaging results. The picture emerging is that solute transfer between the humours and the fibre mass is determined by four processes: (i) paracellular transport of ions, water and small molecules along the intercellular spaces between epithelial and FCs, driven by Na(+)-leak conductance; (ii) membrane transport of such solutes from the intercellular spaces into the fibre cytoplasm by specific carriers and transporters; (iii) gap-junctional coupling mediating solute flux between superficial and deeper fibres, Na(+)/K(+)-ATPase-driven efflux of waste products in the equator, and electrical coupling of fibres; and (iv) transcellular transfer via caveoli and coated vesicles for the uptake of macromolecules and cholesterol. There is evidence that the Na(+)-driven influx of solutes occurs via paracellular and membrane transport and the Na(+)/K(+)-ATPase-driven efflux of waste products via gap junctions. This micro-circulation is likely restricted to the superficial cortex and nearly absent beyond the zone of organelle loss, forming a solute exchange barrier in the lens.
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Affiliation(s)
- Ralf Dahm
- Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria.
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42
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Marzec E, Olszewski J, Grześkowiak E, Kamińska A, Bienert A, Iwanik K. Dielectric studies of the paracetamol–lenticular tissue interactions. Colloids Surf B Biointerfaces 2011; 84:131-4. [DOI: 10.1016/j.colsurfb.2010.12.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 12/20/2010] [Accepted: 12/21/2010] [Indexed: 10/18/2022]
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43
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Maeda S, Tsukihara T. Structure of the gap junction channel and its implications for its biological functions. Cell Mol Life Sci 2011; 68:1115-29. [PMID: 20960023 PMCID: PMC11114897 DOI: 10.1007/s00018-010-0551-z] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 09/28/2010] [Accepted: 09/30/2010] [Indexed: 12/16/2022]
Abstract
Gap junctions consist of arrays of intercellular channels composed of integral membrane proteins called connexin in vertebrates. Gap junction channels regulate the passage of ions and biological molecules between adjacent cells and, therefore, are critically important in many biological activities, including development, differentiation, neural activity, and immune response. Mutations in connexin genes are associated with several human diseases, such as neurodegenerative disease, skin disease, deafness, and developmental abnormalities. The activity of gap junction channels is regulated by the membrane voltage, intracellular microenvironment, interaction with other proteins, and phosphorylation. Each connexin channel has its own property for conductance and molecular permeability. A number of studies have tried to reveal the molecular architecture of the channel pore that should confer the connexin-specific permeability/selectivity properties and molecular basis for the gating and regulation. In this review, we give an overview of structural studies and describe the structural and functional relationship of gap junction channels.
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Affiliation(s)
- Shoji Maeda
- Institute for Protein Research, Osaka University, OLABB, 6-2-3 Furuedai, Suita, 565-0874 Japan
- Department of Life Science, University of Hyogo, 3-2-1 Koto, Kamighori, Akoh, Hyogo 678-1297 Japan
- Present Address: Paul Scherrer Institut, Biology and Chemistry OFLG 101, 5232 Villigen, Switzerland
| | - Tomitake Tsukihara
- Institute for Protein Research, Osaka University, OLABB, 6-2-3 Furuedai, Suita, 565-0874 Japan
- Department of Life Science, University of Hyogo, 3-2-1 Koto, Kamighori, Akoh, Hyogo 678-1297 Japan
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44
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Tao L, DeRosa AM, White TW, Valdimarsson G. Zebrafish cx30.3: identification and characterization of a gap junction gene highly expressed in the skin. Dev Dyn 2011; 239:2627-36. [PMID: 20737512 DOI: 10.1002/dvdy.22399] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
We have identified and characterized a zebrafish connexin, Cx30.3. Sequence similarity analyses suggested that Cx30.3 was orthologous to both mammalian Cx26 and Cx30, known to play important roles in the skin and inner ear of mammals. Analysis of mRNA expression showed that Cx30.3 was present in early embryos, and was highly abundant in skin, but also detected in other tissues including fins, inner ear, heart, and the retina. Injection of Cx30.3 cRNA into Xenopus oocytes elicited robust intercellular coupling with voltage gating sensitivity similar to mammalian Cx26 and Cx30. The similarities in functional properties and expression patterns suggest that Cx30.3, like mammalian Cx26 and Cx30, may play a significant role in skin development, hearing, and balance in zebrafish. Thus, zebrafish could potentially serve as an excellent model to study disorders of the skin and deafness that result from human connexin mutations.
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Affiliation(s)
- Liang Tao
- Department of Biological Sciences, University of Manitoba, Winnipeg, Canada
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45
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Sánchez HA, Mese G, Srinivas M, White TW, Verselis VK. Differentially altered Ca2+ regulation and Ca2+ permeability in Cx26 hemichannels formed by the A40V and G45E mutations that cause keratitis ichthyosis deafness syndrome. ACTA ACUST UNITED AC 2011; 136:47-62. [PMID: 20584891 PMCID: PMC2894548 DOI: 10.1085/jgp.201010433] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mutations in GJB2, which encodes Cx26, are one of the most common causes of inherited deafness in humans. More than 100 mutations have been identified scattered throughout the Cx26 protein, most of which cause nonsyndromic sensorineural deafness. In a subset of mutations, deafness is accompanied by hyperkeratotic skin disorders, which are typically severe and sometimes fatal. Many of these syndromic deafness mutations localize to the amino-terminal and first extracellular loop (E1) domains. Here, we examined two such mutations, A40V and G45E, which are positioned near the TM1/E1 boundary and are associated with keratitis ichthyosis deafness (KID) syndrome. Both of these mutants have been reported to form hemichannels that open aberrantly, leading to “leaky” cell membranes. Here, we quantified the Ca2+ sensitivities and examined the biophysical properties of these mutants at macroscopic and single-channel levels. We find that A40V hemichannels show significantly impaired regulation by extracellular Ca2+, increasing the likelihood of aberrant hemichannel opening as previously suggested. However, G45E hemichannels show only modest impairment in regulation by Ca2+ and instead exhibit a substantial increase in permeability to Ca2+. Using cysteine substitution and examination of accessibility to thiol-modifying reagents, we demonstrate that G45, but not A40, is a pore-lining residue. Both mutants function as cell–cell channels. The data suggest that G45E and A40V are hemichannel gain-of-function mutants that produce similar phenotypes, but by different underlying mechanisms. A40V produces leaky hemichannels, whereas G45E provides a route for excessive entry of Ca2+. These aberrant properties, alone or in combination, can severely compromise cell integrity and lead to increased cell death.
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Affiliation(s)
- Helmuth A Sánchez
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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46
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Liu J, Xu J, Gu S, Nicholson BJ, Jiang JX. Aquaporin 0 enhances gap junction coupling via its cell adhesion function and interaction with connexin 50. J Cell Sci 2010; 124:198-206. [PMID: 21172802 DOI: 10.1242/jcs.072652] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Both connexin 50 (Cx50) and aquaporin 0 (AQP0) have important roles in lens development and homeostasis, and their mutations are associated with human congenital cataracts. We have previously shown that Cx50 directly interacts with AQP0. Here, we demonstrate the importance of the Cx50 intracellular loop (IL) domain in mediating the interaction with AQP0 in the lens in vivo. AQP0 significantly increased (~20-30%) the intercellular coupling and conductance of Cx50 gap junctions. However, this increase was not observed when the IL domain was replaced with those from other lens connexins. The Cx50-AQP0 interaction had no effect on Cx50 hemichannel function. A fusion protein containing three extracellular loop domains of AQP0 efficiently blocked the cell-to-cell adhesion of AQP0 and attenuated the stimulatory effect of AQP0 on Cx50 gap junction conductance. These data suggest that the specific interaction between Cx50 and AQP0 enhances the coupling of Cx50 gap junctions, but not hemichannels, through the cell adhesion function of AQP0. This result establishes a physiological role of AQP0 in the functional regulation of gap junction channels.
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Affiliation(s)
- Jialu Liu
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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47
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Abstract
Gap junctions are aggregates of intercellular channels that permit direct cell-cell transfer of ions and small molecules. Initially described as low-resistance ion pathways joining excitable cells (nerve and muscle), gap junctions are found joining virtually all cells in solid tissues. Their long evolutionary history has permitted adaptation of gap-junctional intercellular communication to a variety of functions, with multiple regulatory mechanisms. Gap-junctional channels are composed of hexamers of medium-sized families of integral proteins: connexins in chordates and innexins in precordates. The functions of gap junctions have been explored by studying mutations in flies, worms, and humans, and targeted gene disruption in mice. These studies have revealed a wide diversity of function in tissue and organ biology.
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48
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Tandem alternative splicing of zebrafish connexin45.6. Genomics 2010; 96:112-8. [PMID: 20466054 DOI: 10.1016/j.ygeno.2010.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 04/19/2010] [Accepted: 05/04/2010] [Indexed: 11/24/2022]
Abstract
Early studies suggested that most connexin genes share a relatively simple structure with a single intron of variable length interrupting the 5' untranslated region (UTR). Here we report that zebrafish cx45.6 shows six isoforms of alternative 5'UTRs which are generated from multiple promoter usage and alternative pre-mRNA splicing. Interestingly, cx45.6 undergoes tandem alternative splicing, which produces transcripts only differing by 3 nucleotides. This is the first study that has demonstrated tandem alternative pre-mRNA splicing in the connexin gene family. Expression patterns of cx45.6 alternative transcripts were demonstrated by real-time RT-PCR during zebrafish embryonic development and in adult tissues. The complexity of 5'UTR diversity suggests complicated regulatory mechanisms for cx45.6 gene expression at both transcriptional and post-transcriptional levels, and we propose that tandem alternative splicing in cx45.6 5'UTRs could play a role in translational control. These results lay groundwork for further investigations on the regulation and function of cx45.6 gene expression.
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49
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Niger C, Hebert C, Stains JP. Interaction of connexin43 and protein kinase C-delta during FGF2 signaling. BMC BIOCHEMISTRY 2010; 11:14. [PMID: 20338032 PMCID: PMC2855512 DOI: 10.1186/1471-2091-11-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Accepted: 03/25/2010] [Indexed: 01/07/2023]
Abstract
Background We have recently demonstrated that modulation of the gap junction protein, connexin43, can affect the response of osteoblasts to fibroblast growth factor 2 in a protein kinase C-delta-dependent manner. Others have shown that the C-terminal tail of connexin43 serves as a docking platform for signaling complexes. It is unknown whether protein kinase C-delta can physically interact with connexin43. Results In the present study, we investigate by immunofluorescent co-detection and biochemical examination the interaction between Cx43 and protein kinase C-delta. We establish that protein kinase C-delta physically interacts with connexin43 during fibroblast growth factor 2 signaling, and that protein kinase C delta preferentially co-precipitates phosphorylated connexin43. Further, we show by pull down assay that protein kinase C-delta associates with the C-terminal tail of connexin43. Conclusions Connexin43 can serve as a direct docking platform for the recruitment of protein kinase C-delta in order to affect fibroblast growth factor 2 signaling in osteoblasts. These data expand the list of signal molecules that assemble on the connexin43 C-terminal tail and provide a critical context to understand how gap junctions modify signal transduction cascades in order to impact cell function.
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Affiliation(s)
- Corinne Niger
- Department of Orthopaedics, University of Maryland, School of Medicine, Baltimore, MD, USA
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50
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Mathias RT, White TW, Gong X. Lens gap junctions in growth, differentiation, and homeostasis. Physiol Rev 2010; 90:179-206. [PMID: 20086076 DOI: 10.1152/physrev.00034.2009] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The cells of most mammalian organs are connected by groups of cell-to-cell channels called gap junctions. Gap junction channels are made from the connexin (Cx) family of proteins. There are at least 20 isoforms of connexins, and most tissues express more than 1 isoform. The lens is no exception, as it expresses three isoforms: Cx43, Cx46, and Cx50. A common role for all gap junctions, regardless of their Cx composition, is to provide a conduit for ion flow between cells, thus creating a syncytial tissue with regard to intracellular voltage and ion concentrations. Given this rather simple role of gap junctions, a persistent question has been: Why are there so many Cx isoforms and why do tissues express more than one isoform? Recent studies of lens Cx knockout (KO) and knock in (KI) lenses have begun to answer these questions. To understand these roles, one must first understand the physiological requirements of the lens. We therefore first review the development and structure of the lens, its numerous transport systems, how these systems are integrated to generate the lens circulation, the roles of the circulation in lens homeostasis, and finally the roles of lens connexins in growth, development, and the lens circulation.
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Affiliation(s)
- Richard T Mathias
- Department of Physiology and Biophysics, SUNY at Stony Brook, Stony Brook, New York 11794-8661, USA.
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